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New Implanted Devices May Reshape Medicine

UT Dallas Team Helps Create Transistors That Wrap Around Tissues

May 13, 2014

Researchers from The University of Texas at Dallas and the University of Tokyo have created electronic devices that become soft when implanted inside the body and can deploy to grip 3-D objects, such as large tissues, nerves and blood vessels.

These biologically adaptive, flexible transistors might one day help doctors learn more about what is happening inside the body, and stimulate the body for treatments.

When heated, the devices can change shape and still maintain their electronic properties. Click here to watch the transistor flex its gripping ability.

The research, available online and in an upcoming print issue of Advanced Materials, is one of the first demonstrations of transistors that can change shape and maintain their electronic properties after they are implanted in the body, said Jonathan Reeder BS’12, a graduate student in materials science and engineering and lead author of the work.

“Scientists and physicians have been trying to put electronics in the body for a while now, but one of the problems is that the stiffness of common electronics is not compatible with biological tissue,” he said. “You need the device to be stiff at room temperature so the surgeon can implant the device, but soft and flexible enough to wrap around 3-D objects so the body can behave exactly as it would without the device. By putting electronics on shape-changing and softening polymers, we can do just that.”

Dr. Walter Voit

Shape memory polymers developed by Dr. Walter Voit, assistant professor of materials science and engineering and mechanical engineering and an author of the paper, are key to enabling the technology.

The polymers respond to the body’s environment and become less rigid when they’re implanted. In addition to the polymers, the electronic devices are built with layers that include thin, flexible electronic foils first characterized by a group including Reeder in work published last year in Nature.

The Voit and Reeder team from the Advanced Polymer Research Lab in the Erik Jonsson School of Engineering and Computer Science fabricated the devices with an organic semiconductor but used adapted techniques normally applied to create silicon electronics that could reduce the cost of the devices.

“We used a new technique in our field to essentially laminate and cure the shape memory polymers on top of the transistors,” said Voit, who is also a member of the Texas Biomedical Device Center. “In our device design, we are getting closer to the size and stiffness of precision biologic structures, but have a long way to go to match nature’s amazing complexity, function and organization.”

“Our research comes from a different angle and demonstrates that we can engineer a device to change shape in a more biologically compatible way.”

Jonathan ReederBS'12, graduate student

The rigid devices become soft when heated. Outside the body, the device is primed for the position it will take inside the body.

During testing, researchers used heat to deploy the device around a cylinder as small as 2.25 millimeters in diameter, and implanted the device in rats. They found that after implantation, the device had morphed with the living tissue while maintaining excellent electronic properties.

“Flexible electronics today are deposited on plastic that stays the same shape and stiffness the whole time,” Reeder said. “Our research comes from a different angle and demonstrates that we can engineer a device to change shape in a more biologically compatible way.”

The next step of the research is to shrink the devices so they can wrap around smaller objects and add more sensory components, Reeder said.

UT Dallas researchers and materials engineers Taylor Ware, David Arreaga-Salas and Adrian Avendano-Bolivar were also involved in the study. Ware completed his PhD in 2013 and performs fundamental research on liquid crystalline polymers at the Air Force Research Labs.

Graduate student Jonathan Reeder

Student Finds Dream Work

When Jonathan Reeder transferred to UT Dallas as an undergraduate student, he said he had two dreams: baseball and engineering.

“So I picked a school that was very good at engineering, but also had a baseball team,” he said.

He now dreams of continuing in academia after completing his PhD, thanks to opportunities to conduct research as an undergraduate with Dr. Walter Voit.

Before taking Voit’s classes, “I was not even interested in research,” he said. “In his lab, I was able to pursue things I found interesting and work at my own pace. There was this general excitement about discovering new scientific advances and doing things that had not been done before.”

Reeder, who also played for the UT Dallas baseball team, was one of five students in the first graduating class of mechanical engineering. The summer after graduation, he went to Japan as part of the National Science Foundation East Asia and Pacific Summer Institute, and was awarded a National Science Foundation Graduate Research Fellowship.

Last summer while in Japan, he was a co-author of work published in the scientific journal Nature. That work focused on the fabrication of electronic circuits that are lighter than a feather, could be crumpled like paper and still retain their electrical properties.

“A couple of years ago, I never would have imagined I would be at this point, working with incredibly smart and driven people like Dr. Voit who enabled these opportunities,” Reeder said. “It is exciting and even more motivating.”